A review of reservoir carbon Cycling: Key Processes, influencing factors and research methods

• Reservoirs have carbon source/ sink functions serving as sites for carbon flow and exchange. • The carbon cycle process in reservoirs is influenced by multi-factor mechanisms. • Future research directions for global reservoir carbon cycle include long-term, large-scale monitoring and modeling. Based on the focus on the role of reservoirs as carbon sources and sinks, this article explores their impact on the global carbon cycle. Reservoirs, which are “artificial lakes” created by human activities in rivers, are reviewed in terms of the key links in carbon cycling within reservoir areas, the influencing factors, and research methods related to carbon cycling and carbon emissions. By reviewing the literature on reservoir carbon cycling, we elucidate the mechanisms of carbon inputs, decomposition and transformation, carbon emissions, and carbon burial, summarizing the biogeochemical coupling processes of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), particulate organic carbon (POC), and particulate inorganic carbon (PIC) with hydrological conditions and nutrients. The study concludes that the reservoir carbon cycling process is influenced by the characteristics of the reservoirs themselves, hydrological and hydrodynamic conditions, physicochemical and nutrient conditions, and human activities. Additionally, we further clarify the applications of field sampling and analysis, modeling, remote sensing technology, and isotope techniques in reservoir carbon cycling. In the future, it is recommended to continue monitoring and simulating the reservoir carbon cycle processes on a long-term and large-scale basis, and to deeply explore the multifactorial mechanisms of reservoir construction in the global carbon cycle.